This invention relates to a method and system for using the tide to generate power.
Numerous tide-operated systems have been developed in the prior art. These have proved to be impractical and uneconomical to operate. For example, each of the systems disclosed in U.S. Pat. No. 3,487,228 to Kriegel, Dec. 30, 1969; U.S. Pat. No. 3,515,889 to Kammerer, June 2, 1970; U.S. Pat. No. 4,208,878 to Rainey, June 24, 1980; and Patent No. P23 65 197.0 of the Federal Republic of Germany, published Oct. 7, 1975 includes a conventional type pump which introduces a substantial element of friction into the system. Moreover, the system disclosed in U.S. Pat. No. 3,567,953, issued to Lord, Mar. 2, 1971 comprises a complex system of gears which also introduces a substantial amount of friction into the system. Another prior art system, such as that disclosed by Tsubota in U.S. Pat. No. 4,258,269, issued Mar. 24, 1981, relies for operation of a turbine water transfer and siphon action in a series of small diameter conduits responsive to differential in the water level in adjacent chambers. This also introduces friction and surface tension into the system, and substantially limits the volume of liquid which can be used to drive the system.
It is therefore the object of the present invention to provide an improved method and system for using the rise and fall of the tides to generate power, more particularly, in an arrangement substantially free of friction and surface tension which contemplates the raising large volumes of liquid, to provide a head enabling continuous operation by gravity flow.
These and other objects are realized in a system comprising of a plurality of sets of containers and plungers, disposed in coaxial arrangement to move in telescoping relation with the rise and fall of the tide.
The invention contemplates at least two vertically-disposed hollow containers, open at the top, each enclosing a plunger in coaxial relation. One container, and the plunger in the other container, are movable, being connected together to move up and down with the tide; whereas the other container and the plunger in one container are fixed. Each container is partially filled with liquid which moves through a closed internal circuit. When the tide rises, the movable container moves up, causing a check valve to close, and compressing enclosed liquid against the fixed plunger, thereby forcing the liquid to move up in the annular space between the fixed plunger and the movable container, overflowing into a first annular trough surrounding its upper end. When the tide falls, the movable plunger moves down in the fixed container, causing a check valve to close, and compressing the enclosed liquid against the fixed container bottom, thereby forcing the liquid to move up in the annular space between the movable plunger and the fixed container, overflowing into a second annular trough surrounding its upper end. The two annular troughs are interconnected by gravity flow through an internal liquid circuit, which incorporates a turbine through which the liquid from one or the other of the annular troughs is constantly forced to flow by the rise and fall of the tide. Liquid pressure forces open each of the check valves at the appropriate time to permit the liquid to return to a respective container. One disclosed embodiment comprises four containers in a symmetrical cruciform array. In another embodiment, a fixed outer container is arranged in coaxial relation to a fixed internal plunger, with an intermediate coaxial structure interposed between the two to serve in the dual capacity of a plunger for the outer fixed container, and a container for the inner fixed plunger.
Also enclosed as a component which greatly enhances the operation of any of the disclosed systems of the present invention is a positive action check valve which is designed to function in response to low pressure differentials. This includes a housing having intake and exhaust conduits leading to and from an inner chamber of substantially circular cross-section which is separated into intake and exhaust sections by a rigid diametrical partition. This includes a central bolt hole surrounded by a plurality of smaller openings symmetrically spaced-apart. A screen is disposed flush against the partition face on the intake side, and a flexible annular diaphragm is held against the face of the partition directed toward the output conduit so that in closed position the diaphragm acts as a flap valve. A bolt is fastened from the center of the screen through the center hold of the partition, and terminates in a conical plug with its apex directed from the face of the partition facing the exhaust conduit. The inner periphery of the annular diaphragm rests on the conical wall of the plug, from which it is displaced to open outwardly or inwardly in response to a small pressure differential between the input and exhaust conduits.
One advantage of the present system is that the turbine is continuously operated with both the rise and fall of the tide.
A further advantage of the present invention over prior art is its simplicity, and the absence of mechanical parts, such as pumps, requiring maintenance.
A further advantage of the present invention is that it contemplates the lifting of a large volume of liquid in an arrangement substantially free from friction or surface tension, to provide a substantial "head" which operates through gravity flow to generate power.
Another advantage is that a closed circuit system permits driving the turbine with any desired liquid other than sea water which can be very corrosive and abrasive.
These and other objects, features, and advantages, will be apparent from a detailed study of the description hereinafter with reference to the appended drawings.